Finite element formulation of laser material interaction accounting for geometry evolution

Abstract

Laser subtractive and additive manufacturing holds tremendous potential to create intricate parts in small batches. However, due to the complexity of the process physics, it is not currently possible to predict a priori the accuracy of the part geometry or material quality. Numerical simulation with the capability of providing insightful prediction to reassure partprecision and quality in advance is desired, where numerical accuracy and computational performance are equally important aspects to consider. This thesis focuses on developing a generalized finite element framework to simulate the laser-material interaction process, including additive manufacturing (powder bed fusion) and subtractive manufacturing (pulsed laser ablation). In this work, evolution of the part geometry is predicted. For the laser grooving process, material ablation is calculated and the moving material front is tracked under a pulsed laser source. For the Laser Powder Bed Fusion (LPBF) process, the melt pool dimension is computed and its boundary is tracked as the new powder layers are added to the build plate. State variable fields are introduced to solve the phase change physics. Numerical parameters are defined as a priori by a calibration step. Powder consolidation is considered and deformation is accounted by updating the reference configuration. A method is implemented to track the moving material front for multilayer simulation. LPBF experiment samples with multiple powder layers are imaged and quality is correlated to processing parameters based on an analytical model, and further used to validate the finite element simulation result. A three-dimensional transient parallel finite element model is developed for laser grooving and LPBF processes, which may be extended to the entire manufacturing process that enables direct comparison to experiments.